SpinOffs

Turbine inlet temperature is one of the most critical parameters in the Brayton cycle of gas turbine engines. One way to increase the cycle efficiency is to increase the turbine inlet temperature, as illustrated in Figure 1. Here, a typical Brayton cycle T-S diagram chart visualizes the impact of higher turbine inlet temperatures on higher efficiency. Indeed, the area between the solid curves through points 0-3-4-8 represents the useful power generated by the turbine. The cycle efficiency can be calculated by dividing this area by the total area below curve 3-4, being the heat input. The dash lines convey the cycle with increased turbine inlet temperature, and the new cycle efficiency is the area in 0-3’-4’-8 curves divided by the area below curve 3’-4’. It is easy to see how a higher turbine inlet temperature increases cycle efficiency. Because of pursuing higher efficiency in modern gas turbine engine design, turbine inlet temperature has been pushed to a level that most material cannot withstand without effective cooling. Figure 2 shows the increasing trend of turbine inlet temperature since the 1940’s. Since the 1970’s, the turbine inlet temperature has been above material capability through the introduction of turbine cooling techniques.

There is obviously a huge amount of interest in Supercritical Carbon Dioxide (sCO₂) within the energy industry. One reason is because sCO₂ Brayton power cycles operate in the same way as other Brayton cycles, but with a much higher power density. This has the potential for greatly reducing the size and cost of equipment. Additionally, efficiencies can reach as high as 40% for an sCO₂ system, compared to about 33% for a typical heat recovery system. 

Perhaps it is because Spring is so slow to come this year, but I have been thinking a lot about refrigeration and the different types of systems there are. Refrigeration systems that operate below 120 K are commonly referred to as cryocoolers. Figure 1 illustrates the most common usage of cryocoolers in the fields of superconductivity, liquefaction, and infrared sensors. As you can see, cryocoolers cover a wide range in temperatures, cooling loads, and applications.

The 2015 Paris Climate Talks (COP21) were successful in achieving consensus from 196 countries that climate change must be given significant attention. There was a particular focus on the release of carbon, in the form of carbon dioxide and carbon monoxide, as something that must be curtailed.